Management device, and electricity storage system

Abstract

A cell voltage measurement unit measures a voltage of each of a plurality of cells that are series-connected. A total voltage measurement unit measures a total voltage of the plurality of cells. A controller manages an internal impedance of each of the plurality of cells. The controller detects a ripple of the total voltage measured by the total voltage measurement unit, estimates a ripple of each cell voltage by multiplying the detected ripple of the total voltage by a ratio of the internal impedance of each cell to a resultant internal impedance of the plurality of cells, and determines whether the ripple of each cell voltage is within an allowable voltage range.

The invention claimed is: 
     
       1. A management device comprising:
 a cell voltage measurement unit that measures a voltage of each cell of a plurality of cells that are series-connected; 
 a total voltage measurement unit that measures a total voltage of the plurality of cells; and 
 a controller that manages an internal impedance of each cell of the plurality of cells, 
 wherein the controller detects a ripple of the total voltage measured by the total voltage measurement unit, estimates a ripple of each cell voltage by multiplying the ripple, which is detected, of the total voltage by a ratio of the internal impedance of each cell to a resultant internal impedance of the plurality of cells, and determines whether the ripple of each cell voltage is within an allowable voltage range. 
 
     
     
       2. A management device comprising:
 a cell voltage measurement unit that measures a voltage of each cell of a plurality of cells that are series-connected; 
 a ripple detector that detects a ripple of a cell voltage of a part of the plurality of cells; 
 a controller that manages an internal impedance of each cell of the plurality of cells, 
 wherein the controller estimates a ripple of each cell voltage, based on the ripple of the voltage detected by the ripple detector and on the internal impedance of each of the plurality of cells, and determines whether the ripple of each cell voltage is within an allowable voltage range. 
 
     
     
       3. The management device according to  claim 2 , wherein the ripple detector is disposed on the controller. 
     
     
       4. The management device according to  claim 1 , wherein the controller manages the internal impedance of each cell in a frequency band corresponding to a frequency twice a commercial power source frequency. 
     
     
       5. The management device according to  claim 1 , further comprising:
 a current measurement unit that measures a current flowing through the plurality of cells; and 
 a temperature measurement unit that measures a temperature of the plurality of cells, 
 wherein the controller includes a table where characteristic data of a state of health (SOH), a state of charge (SOC), and an internal impedance of each of the cells at different temperatures is described, and 
 the controller specifies the internal impedance of each cell by referring to the table based on the SOH, the SOC, and the temperature of each cell. 
 
     
     
       6. The management device according to  claim 1 , further comprising a current measurement unit that measures a current flowing through the plurality of cells,
 wherein the controller estimates the internal impedance of each cell based on a voltage change of each cell before and after supplying a predetermined current to the plurality of cells. 
 
     
     
       7. An electricity storage system comprising:
 a plurality of cells that are series-connected; and 
 the management device according to  claim 1  that manages the plurality of cells. 
 
     
     
       8. The management device according to  claim 2 , wherein the controller manages the internal impedance of each cell in a frequency band corresponding to a frequency twice a commercial power source frequency. 
     
     
       9. The management device according to  claim 2 , further comprising:
 a current measurement unit that measures a current flowing through the plurality of cells; and 
 a temperature measurement unit that measures a temperature of the plurality of cells, 
 wherein the controller includes a table where characteristic data of a state of health (SOH), a state of charge (SOC), and an internal impedance of each of the cells at different temperatures is described, and 
 the controller specifies the internal impedance of each cell by referring to the table based on the SOH, the SOC, and the temperature of each cell. 
 
     
     
       10. The management device according to  claim 2 , further comprising a current measurement unit that measures a current flowing through the plurality of cells,
 wherein the controller estimates the internal impedance of each cell based on a voltage change of each cell before and after supplying a predetermined current to the plurality of cells. 
 
     
     
       11. An electricity storage system comprising:
 a plurality of cells that are series-connected; and 
 the management device according to  claim 2  that manages the plurality of cells.